The present invention relates in general to growing carbon films, and in particular, to growing a carbon film on a treated substrate.
Field emission display devices show promise in providing a low cost alternative to LCD displays, especially with respect to laptop computers. Furthermore, field emission devices are beginning to be practically applied in other areas, such as billboard-type display devices.
One of the challenges in producing a good field emission device or display is the manufacture of a field emitter material, which is inexpensive to manufacture yet efficient with respect to power consumption and consistent in its display characteristics. Carbon and/or diamond field emitter materials have shown promise in meeting such constraints.
One of the problems with the present method for fabricating a matrix addressable display using such a film is that in order to pattern the film, one or more lithography and etching steps have to be applied to the film after it has been deposited. Such processes degrade the film""s performance and emission capabilities, often to the point where the film emissions are inadequate. As a result, there is a need in the art for a fabrication process whereby post-deposition processes performed on the film are not utilized.
Furthermore, to make field emission displays economically feasible, there is a need to enhance the field emission properties of the deposited film. Therefore, there is a need in the art for improvements in the emission properties of carbon and diamond-like films.
The foregoing need is addressed by the present invention. A substrate, such as a ceramic or glass, is cleaned and metalized by electron-beam (e-beam) evaporation or sputtering of metals, such as titanium (Ti). A desired metal feedline pattern is then made by conventional photolithography and etching of the metal. This pattern can also be made by metalization through a shadow mask. Emitting areas, or pixels, are then defined by another lithography process. The metal layer in these areas are removed again by etching. Utilizing the same photoresist as a mask, a surface treatment process such as an acid or base etch is then applied, in which the surface morphology and possibly chemical composition (if non-elemental materials are used) of the substrate in the pixel areas are changed. Another thin layer of metal is then further deposited. The photoresist is stripped, leaving only the pixel area treated and the thin metal layer coated. Lastly, a thin layer of emitting carbon film is deposited all over the surface. Since the pixel areas have been treated such that the surface morphology on these areas not only greatly enhances the nucleation, but also the growth of the carbon film, electron emission is promoted from the carbon film at these pixel areas. As a result, even though the carbon film was not patterned, only the pixel areas emit when an electrical field is applied to the film.
An alternative is that no thin metal layer is deposited on the active area; the emitting carbon film is deposited directly onto the treated substrate. This alternative is applicable when each pixel area is small (less than a few hundreds of micrometers square, as an example).
Another alternative is that a surface treatment is applied with or without lithography to the substrate before it is metalized. A metal layer is then deposited onto the substrate with or without any patterning. Carbon film is then deposited. In the instance of no patterning for both active area and metalization, the entire substrate surface will emit electrons effectively, which is useful for such applications as lighting or cold electron sources.
The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.